Substantiation of the shunt failure diagnosis and subsequent consideration of indications for surgical elimination of the malfunction is a laborious and challenging process. Identification of a malfunction in doubtful cases requires, in addition to standard examinations, extra diagnostic procedures, which may delay making a decision for several weeks to several months. The article describes a case of mechanical CSF shunt malfunction (breakage and failure of a peritoneal catheter in a 7-year-old girl) with intracranial hypertension symptoms, but without typical enlargement of the brain ventricles. According to the medical history, congenital hydrocephalus in the child was accompanied by an inflammatory process of bacterial and viral etiology. The absence of brain ventricle enlargement was shown not to exclude a probability of shunt malfunction. In this case, a specific phenomenon, an intraparenchymatous cerebrospinal fluid "lake" surrounding a ventricular catheter, was observed. Shunting recovery did not lead to a significant reduction in the phenomenon size. Causes underlying this phenomenon require further investigation.